1. Technical Field and Industrial Applicability of the Invention
The present invention relates to an apparatus for applying a polymer coating to a substrate, typically a fiber batt, in order to encapsulate the substrate. The encapsulation may be partial or complete and may be applied in combination with other films, sheet materials and facing materials as desired.
2. Background of the Invention
Fibrous insulation is typically manufactured by fiberizing a molten composition of polymer, glass or other minerals to form fine fibers and depositing the fibers on a collecting conveyor to form a batt or a blanket. Although mineral fibers, such as glass fibers, are typically used in insulation products, depending on the particular application organic fibers, such as polypropylene and polyester may be used singly or in combination with mineral fibers.
Most fibrous insulation products also incorporate a binder composition to bond the fibers together where they contact each other within the batt or sheet to form a lattice or network. This lattice structure provides improved resiliency that allows the insulation product to recover a substantial portion of its thickness after being compressed and also provides improved stiffness and handleability. During the manufacturing process the insulation products are typically formed and cut to provide sizes generally compatible with standard construction practices. Some insulation products also incorporate a facing or encapsulating material on at least one of the major surfaces to improve the performance and/or the handling of the batt. In many cases the facing or encapsulating material includes a vapor barrier on at least one major surface, while in other insulation products, such as binderless products, the facing or encapsulating material may significantly improve the product integrity and durability.
Insulation products incorporating a vapor barrier are commonly used to insulate wall, floor or ceiling cavities that separate a warm moist space, typically the living or work spaces, from a cold space, typically the exterior, crawl space, or ground. In such applications, the vapor barrier is preferably placed to prevent warm moist air from diffusing toward the cold space where it would cool and condense within the insulation. Such a situation would result in a damp insulation product that cannot perform at its designed efficiency and may lead to microbial growth within the insulation resulting in health or aesthetic concerns. In predominately warm moist climates, however, it is not uncommon to reverse the typical installation in order to prevent vapor from entering the insulation cavity and approaching an air conditioned space.
There are, however, some applications that require an insulation product that does not incorporate or provide a vapor barrier, but rather allows water vapor to pass through fairly readily. For example, insulation products designed and intended for installation over existing attic insulation should not include a vapor barrier. Similarly, insulation products for wall cavities that have a separate full wall vapor barrier, such as a polyethylene film, applied over the insulation product.
A number of methods for encapsulating fibrous batts for improved handling properties are known. For example, U.S. Pat. No. 5,277,955 to Schelhorn et al. discloses an encapsulated batt in which the encapsulation material is adhered to the batt with an adhesive that can be applied in longitudinal stripes, or in patterns such as dots, or in an adhesive matrix. The Schelhorn patent also discloses that an alternative method of attachment is for the adhesive layer to be an integral part of the encapsulation layer, which, when softened, bonds to the fibers in the batt and is hereby incorporated, in its entirety, by reference.
U.S. Pat. No. 5,733,624 to Syme et al. discloses a mineral fiber batt impregnated with a coextruded polymer layering system, and U.S. Pat. No. 5,746,854 to Romes et al. discloses a method for impregnating a mineral fiber batt with a coextruded film in which at least the coextruded film is heated before being applied to the fiber batt. The heat energy necessary to achieve the necessary degree of heating may be transferred primarily by conduction the coextruded film passes over a heated cylinder or through radiant infrared heaters. Attaching the coextruded film in this manner has some disadvantages in that the particular heating process cannot be abruptly terminated or quickly varied due to the large thermal mass provided by the heated cylinder. In addition, the heated cylinder does not provide a means for selectively heating portions of the coextruded film to different temperatures. These patents are hereby incorporated, in their entirety, by reference.
Many traditional vapor barriers for insulation products comprised a layer of asphalt covered with a layer of kraft paper or a foil facing material. The asphalt layer was generally applied in molten form, covered with the facing material and pressed against the fibrous insulation material as it was cooled to bond the facing material to the fibrous batt. During cold weather installations, working with an asphalt/kraft paper faced fiber batt may be complicated by the increased brittleness of the asphalt adhesive layer. Conversely, during warm weather installations, the asphalt material will tend to soften and become sticky and more likely to foul cutting tools.
U.S. Pat. No. 6,357,504 to Patel et al. provided an alternative means for attaching a facing layer to a fibrous batt in which the facing comprises a coextruded polymer film including both a barrier layer and a bonding layer, with the bonding layer having a softening point lower than the softening point of the barrier layer. The bonding layer could comprise a range of materials including ethylene N-butyl acrylate, ethylene methyl acrylate ethylene ethyl acrylate, low density polyethylene (LDPE) and ethylene vinyl acetate, both singularly and in combination. Accordingly, when the facing is heated to a temperature above the softening point of the bonding layer, but below the softening point of the barrier layer, the facing may be adhered to the batt as the bonding layer attaches to the fibers. This patent is hereby incorporated, in its entirely, by reference.
In addition to facing layers provided on one or more surfaces of a fibrous batt, some prior art applications provide for an encapsulating layer to improve the tactility of the insulation product during the handling and mounting, reduce or eliminate the release of fibers before, during or after mounting and improved tensile strength. One such method is disclosed in U.S. Pat. No. 6,203,646 to Gundberg et al. in which the encapsulating layer is formed directly on the surface of the fiber batt by forming a thermoplastic polymer melt distributing fibers formed from the polymer melt onto the fiber batt. In this method, the adhesive characteristics of the molten and partially molten thermoplastic polymers is used to adhere the layer to the underlying fibers without the use of any additional binder or adhesive composition. This patent is hereby incorporated, in its entirety, by reference.
Another method and apparatus for providing a melt blown encapsulating layer on a fiber batt is provided in U.S. Pat. No. 5,501,872 to Allen et al. in which a six-sided fibrous batt is coated with a nonwoven polymeric material by passing the batt sequentially through three coating stations. Four sides of the batt are coated in the first two stations and, after the batt is turned 90°, the final two sides are coated to completely encapsulate the batt in a fibrous nonwoven coating layer. This patent is hereby incorporated, in its entirety, by reference.
There still, however, remains a need for improved methods for encapsulating insulation products to enhance their handling and performance encapsulation methods.